1. Field
The present specification generally relates to systems and methods for treating air streams, such as those exhausted by firing kilns during the firing of ceramic honeycomb substrates.
2. Technical Background
Manufacturing processes for ceramic honeycomb filters such as those used to manufacture diesel particulate filters (e.g., firing processes) may produce undesirable waste pollutants as by-products. Such pollutants may include volatile organic compounds (“VOCs”), carbon monoxide (CO), and hydrogen fluoride, for example. These pollutants may be emitted during the firing process in which the ceramic material is subjected to high temperatures. Because governments place limits on the amount of pollutants that may be released into the environment, the pollutants within the air stream created by the firing process need to be removed from the air stream prior to releasing the air stream to the atmosphere.
Thermal oxidizers, such as recuperative thermal oxidizers and catalytic thermal oxidizers, are treatment devices that may be integrated into firing kiln exhaust systems to destroy VOCs and CO in an air stream created during the firing process. Certain thermal oxidizers may require an operating temperature range of about 300° C. to about 650° C. to effectively destroy VOCs and CO that may be present in the air stream. Because of this high operating temperature, these treatment devices require one or more external heating sources, such as a burner, to raise the temperature of the air stream (with pollutants) entering the thermal oxidizer. However, the use of an auxiliary burner or burners to heat the exhaust air stream adds substantial energy costs to the manufacturing process.
Accordingly, a need exists for alternative systems and methods of treating air streams exhausted by firing kilns during the firing process.